Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$160.74	5.248%	$169.1756	$169.18	$169.20	$169.20
Purchase #2	$5.53	3.574%	$5.7276	$5.73	$5.75	$5.70
Purchase #3	$93.48	7.134%	$100.1489	$100.15	$100.15	$100.10
Purchase #4	$18.74	9.855%	$20.5868	$20.59	$20.60	$20.60
Purchase #5	$190.64	10.455%	$210.5714	$210.57	$210.55	$210.60
Purchase #6	$12.81	12.841%	$14.4549	$14.45	$14.45	$14.50
Purchase #7	$67.93	4.845%	$71.2212	$71.22	$71.20	$71.20
7 purchase totals =	$549.87		$591.8864	$591.89	$591.90	$591.90